smith



July 6, 1926. 1,591,930 W. A. SMITH BALANCED ANVIL BLOCK Filed Juqe'20,1925 INVENTOR. lf fiaormfimifi H15 ATT NEYS.

Patented July 5, 13926.

UNITED sT re-s SPA-TENT e rrii ce.

WILLlIAM-A. SMITH, OF ATHENS PENNSYLVANIA, ASSIGNOR TO INGERSOLL-RANDCOMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

BALANCED ANVILI BLOCK.

Application filed June 20, 1925. Serial 'No. 38;476.

This invention relates to fluid "actuated rock drills, butinoreparticularly to thejpercussive element of certain types of rock drills.in which a member or anvil block is interposedslidably between thehammer pis-' ton and the-drill steel for transmitting the blows of thepiston -'to the drill steel.

l leretofore in =drills of this type, considerable annoyance has beencaused by the tendency-of the drill to recoil fron'rt-he work ata-certain "point-during the cycle of opera tions. This isparticularlythecase in hand held machines in which the recoil of thedrill istransmitteddirectly to the operator.

ft is-accordi-ngly an object-of this invention to eliminate the tendencyof a rock drill t'o recoil from the work ata certain period during thecycle of operation.

@ther objects will 'be in part obvious and in part pointed'outhereinafter.

The invention consists :of the combinations of elements, features of:construction 1 and arrangement of parts having the general mode ofoperation, substantially as hereinafter described andmore particularlypointed out '111 the appended claims and lllustrated in the accompanyingdrawings.

The drawing' showsa rock drill in elevation sectioned longitudinally,illustrating one embodiment which the invention imay'assnmeli'npractice.

Referring more particularly to the drawing, the invention is shownembodied in a rock drill of the hand held type, having a cylinder A anda piston B adapted to reciprocate within the cylinder. A front cylinderwasher C is supported within the front end of the cylinder A and servesas a closure for said front end. The back end of the cylinder is sealedby a back head D which in this instance is provided with a bore E toform an extension to a reduced rearward bore F of the cylinder. A fronthead Gr isv arranged at the front end of the drill to receive slidably ahollow drill steel H. In this instance, the front head iscentralizedwith the front cylinder washer O by means of a flanged bushing J. Theparts comprising the drill casing, namely the cylinder A, the

back head D, the front cylinder washer C, the front head G and theflanged bushing J may be held in operative position with respect to eachother by any suitable and con- 'venient means such as for instance, siderods v(not shown) which may be arranged on ophead 19 and constantpressure is maintained in the bore F. In this instance, :the admis sionof pressure fluid through a passage A to the backend o'f'the cylinderiscontrolled iy airextension L of the piston 13 andthe-admission ofpressure fluid to the front cnd of the cylinder is controlled by a spoolvalve operative within a bushing P inserted in a suitable bore Qforn'iedin the rearward por tion of the cylinder A. The valveflO is so arrangedwith respect toithe 'bore F that when the piston B nears the end of itsforward stroke, a passageRis uncovered by the extension L to admitpressure fluid into the bushing P for unseating the valve, whereuponpressure fluid passes from the bore througha passage-S to :the front endof the cylinder for returning the ipiston B. A free exhaust T =ispreferably formed intermediate .the ends of the cylinderand] iscontrolled by the piston 13.

In :accordance with. the present invention, the front cylinder washcriGis provided with an enlarged :bore U which :forms a pressure chamber andcommunicates wvith #the front supply passage fs throughazpa-ssage V. Disposed within the front icylinder washer C :is an anvil block W fortransmitting the blows of the piston B to the drill steel H. In thisinstance, the anvil block W is provided with front and rear extensions Xand Y respectively, said extensions being preferably of substantiallyequal diameter.

Means are provided for holding the anvil block against its seat duringthe period when pressure fluid is admitted to the front end of thecylinder. To this end a collar Z is formed on said block to provide aforward actuating and holding face I), said face being preferably of thesame area as the impact face of the anvil block. In order to prevent theforming of a cushion between the collar Z of the anvil block and itsseat, a vent 0 is formed in the washer C to enable the pressure fluidleaking into the back end of the chamber U to escape to atmosphere.

Ordinarily in machines of this type, the pressure to the machinenecessary foreflicient drilling is supplied by the operator by pressing.downwardly on the drill. By so doing, the drill steel is projected intothe front head against the anvil block W and tends to press said anvilblock to its seat. In this position of the anvil block the rearwardextension Y projects well into the front end of the cylinder A and intothe path of the piston. However, with the parts in this position and atthe time that pressure fluid is admitted into the front end of thecylinder, the expansion of'the pressure fluid acting against the face lVof the anvil block and the front face of the piston B tends to raise thedrill casing and consequently moves the anvil bloclc 'W forwardly withrespect to the cylinder, so that when the piston B is again drivenforwardly, the effect of its blows will be greatly reduced. By thisinvention this objectionable feature has been entirely eliminated, anddue to the fact that pressure fluid is admitted to the chamber Usimultaneously with the admission of pressure fluid to the front end ofthe cylinder, and also owing to the fact that the area of the actuatingface Z) snbstantiall y equals the area of the rearward face of theextension Y, the anvil block is at all times in position to receive thefull effect of the blow of the hammer piston B. As will be noted fromthe foregoing description, the admission of pressure fluid to thechamber U is intermittent, and since the exhaust of pressure fluid fromsaid chamber takes place simultaneously with the exhaust of pressurefluid from the front end of the cylinder, the full force of the blow ofthe hammer piston may be obtained.

The above described invent-ion has been found to be unusually eflicientin operation. By its use the drilling elfieiency of a machine of thistype may be greatly increased and permits of longer continuous periodsof operation without fatigue 011 the part of the operator as comparedwith drills not provided with this feature. A further advantage is thatthis construction permits of a considerably heavier piston beng employedwithout causing the excessive vibration usually present in machines ofthis type.

I. claim 1. In a fluid actuated rock drill the com hination of acylinder having a supply passage, a rei-iproeatory hammer piston in thec .inder, a hollow front cylinder washer having a pressure chamber incommunication with th supply passage, an anvil block slidable in thewasher and having a rearward face extending into the cylinder, and acollar on said anvil block slidable in the pressure chamber and havingan actuating and holding face against which pressure fluid from thesupply parage may intermittently act for ronnterbal acingpressurefluidactingagainst said rearward face during admission of pressure fluidinto the front end of the cylinder.

2. In a fluid actuated rock drill the combination of a cylinder having afront supply passage a rcriprocatory hammer piston in the cylinder, a.hollow front cylinder washer having a pressure chamber, an anvil blockslidable in the washer and having an impact tat-e extending into thecylinder, a collar on said anvil block. a forward actuating and holdingface of the same area as the impact face, and a passage through thecylinder and the washer connecting the chamber with the supply passageto admit pressure fluid intermittently into said chamber simultaneouslywith the admission of pressure fluid to the front end of the cylinderfor preventing movement of the anvil block during the admission of suchpressure fluid.

In testimony whereof I have signed this specification.

WILLIAM A. SMITH.

-7 Certificate of Correction. W

It is hereby certified that in Letters Patent No. 1,591,930, grantedJuly 6, 1926, upon the application of illiam A. Smith, of Athens,Pennsylvania, for an improvement in Balanced Anvil Blocks, an errorappears requiring correction as follows: The present drawing should becanceled and the drawing containing the figure attached hereto should beinserted therefor as part of the Letters Patent; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of August, A. D. 1926.

[SEAL] M. J. MOORE,

Acting Commissioner of Patents.

:July ,6 1926.

w. A. SMITH BALANCED ANVIL BLOQK Fi led June 20, 925

\ g IN V EN TOR.

mu 'amZI-dmzm H15 AT-TO NEYS.

